1. Field of the Invention
This invention relates to a vapor phase growth apparatus allowing vapor phase growth of a silicon single crystal film on the main surface of a silicon single crystal substrate to proceed therein, and a method of fabricating an epitaxial wafer realized using the same.
2. Description of the Related Art
Silicon epitaxial wafer having a silicon single crystal film (simply referred to as “film”, hereinafter) grown in vapor phase on the main surface of a silicon single crystal substrate (simply referred to as “substrate”, hereinafter) is widely used for electronic devices such as bipolar IC, MOS-IC and so forth. With advancement in micronization of the electronic devices, requirement for flatness of the main surface of the epitaxial wafer in which the devices are fabricated has been becoming more stringent. Causal factors affecting the flatness include flatness of the substrate and distribution of the film thickness. In recent years, single-wafer-type vapor phase growth apparatus has become a mainstream in fabrication of epitaxial wafers having a diameter of 200 mm or more, in place of batch processing of a plurality of wafers. The apparatus holds a single substrate in a horizontally rotating manner in a reaction vessel, while allowing a source gas to flow from one end to the other end of the reaction vessel in a horizontal and unidirectional manner, to thereby proceed vapor phase growth of the film.
One important factor in view of making the resultant film thickness uniform in the above-described single-wafer-type vapor phase growth apparatus is flow rate, or flow rate distribution of the source gas in the reaction vessel. The single-wafer-type vapor phase growth apparatus is generally configured as introducing the source gas through a gas supply duct and through a gas introducing port formed on one end of the reaction vessel, allowing the source gas to flow along the surface of a substrate, and discharging the source gas through a discharging port on the other end of the vessel. In order to reduce non-uniformity in the flow rate in thus-configured vapor phase growth apparatus, proposals have been made on an apparatus having a dispersion plate with a large number of through holes formed therein, disposed on the downstream side of the gas introducing port, and an apparatus having disposed therein a partition plate partitioning the gas flow in the width-wise direction.
Japanese Laid-Open Patent Publication “Tokkaihei” No. 7-193015 discloses a configuration of an apparatus allowing the source gas supplied through the gas introducing port to flow towards the outer peripheral surface of a bank component disposed around a susceptor holding a substrate, so as to supply the source gas onto the surface of a substrate after climbing up the bank component. A basic concept of this method is to diffuse the source gas by allowing the flow thereof to collide against the outer peripheral surface of the bank component, to thereby resolve non-uniformity in the flow rate. Another proposal has been made on this sort of vapor phase growth apparatus having the bank component improved so as to allow the source gas to flow more smoothly towards the susceptor (Japanese Laid-Open Patent Publication “Tokkai” No. 2002-231641). Still another proposal has been made on the vapor phase growth apparatus improved so as to intentionally make variation in the flow of the source gas on both sides of the susceptor (Japanese Laid-Open Patent Publication “Tokkai” No. 2002-198316).
Typical known problems in the vapor phase epitaxial growth of the silicon single crystal film on the silicon single crystal substrate include deformation of patterns. Several factors affecting the pattern deformation have been known, wherein the degree of pattern deformation can be reduced generally by lowering pressure in the reaction vessel so as to increase a diffusion coefficient of HCl gas produced on the surface of the substrate, to thereby depress the etching action by the HCl gas. For this reason, a reduced pressure condition is preferably applied to vapor phase growth on the silicon single crystal substrate having patterns already formed thereon.
Epitaxial growth under a reduced pressure condition using the apparatus such as described in the aforementioned Japanese Laid-Open Patent Publication “Tokkaihei” No. 7-193015 may, however, sometimes encounter a difficulty in obtaining a desired distribution of film thickness.
It is therefore an object of this invention to provide a vapor phase growth apparatus capable of uniformalizing the flow route of the source gas flowing over the silicon single crystal substrate, and a method of fabricating an epitaxial wafer using the same, aiming at ensuring a desirable distribution of film thickness.                Patent Document 1: Japanese Laid-Open Patent Publication “Tokkaihei” No. 7-193015;        Patent Document 2: Japanese Laid-Open Patent Publication “Tokkai” No. 2002-231641; and        Patent Document 3: Japanese Laid-Open Patent Publication “Tokkai” No. 2002-198316.        